1. Field of the Invention
The present invention relates to control valves and more particularly relates to an improved pilot control relay valve utilized to monitor pressure conditions in a pressurized system and to cause the system to shut down in response to detection of operating pressures outside of a predetermined acceptable pressure range. Accurate monitoring is provided for by dual pistioning action hydraulically actuates a visual indicator mounted on the slide valve of said control valve.
2. General Background
A control valve is normally placed in a fluid flow line or a fluid actuator to prevent the flow of fluid until a fluid pressure reaches a predetermined operating range. Control valves known in the art which have been patented include:
______________________________________ U.S. Pat. No. 3,943,974 U.S. Pat. No. 4,240,609 U.S. Pat. No. 4,074,702 U.S. Pat. No. 4,254,799 U.S. Pat. No. 4,194,529 U.S. Pat. No. 4,252,145 U.S. Pat. No. 4,194,719 U.S. Pat. No. 4,252,146 U.S. Pat. No. 4,196,750 U.S. Pat. No. 4,254,798 U.S. Pat. No. 4,203,571 U.S. Pat. No. 4,256,141 U.S. Pat. No. 4,207,924 U.S. Pat. No. 4,263,938 U.S. Pat. No. 4,213,481 U.S. Pat. No. 4,267,862 U.S. Pat. No. 4,215,746 U.S. Pat. No. 4,275,865 U.S. Pat. No. 4,217,934 U.S. Pat. No. 4,237,931 U.S. Pat. No. 4,220,174 U.S. Pat. No. 4,239,058 U.S. Pat. No. 4,234,162 U.S. Pat. No. 3,038,439 U.S. Pat. No. 3,448,228 U.S. Pat. No. 3,109,441 U.S. Pat. No. 3,202,170 U.S. Pat. No. 3,189,277 U.S. Pat. No. 3,769,996 U.S. Pat. No. 3,985,337 ______________________________________
U.S. Pat. Nos. 3,943,974, 4,194,529, 4,074,702, 4,196,750, 4,207,924, 4,239,058, 4,252,145, 4,256,141 and 4,263,938 provide a single elongated housing with a bore extending longitudinally therethrough and containing a slide valve mounted therein. The slide valve and internal components of the housing are not sealed and therefore are exposed to adverse environmental influences such as mud, dirt salt water, and the like. In this regard, frequent maintainence is required on the control valve resulting in a shut down of the main line during such period. Another disadvantage of the prior art is that in using a single housing with a shaft therein to manually reset the slide valve to an outward or displaced position, the shaft itself must be grasped and pulled out, often resulting in bending of the shaft assembly. This manual reset capability increases the possibility of a complete failure of the shaft or bending to a point where it is unable to return to its normal functioning position. A further disadvantage of the prior art is that these contol valves use a latching pin which provides for a manual detent means when depressed which actually engages the slide valve, and, in extended operations wears a groove therein, the groove eventually becoming rounded to a point that the detent pin begins to slip and fail in its intended function. The wearing can also lead to O-ring slippage destroying the systems integrity. Another disadvantage of prior art is that the indicator means, as with the internal components, is exposed to adverse environmental conditions by being externally mounted on the slide valve. This external mounting also leads to abuse during the manual resetting of the slide valve. Also, when the indicator is malfunctioning and needs replacement, the entire control valve becomes inoperable and the main line it is controlling must be shut down.
A further disadvantage of the prior art is the use of a fluid passageway extending longitudinally within the slide valve to direct fluid from the pilot port to the indicator means to actuate the indicator in that the passageway can be blocked or provide an uneven pressure distribution thus resulting in a "false" indication of the operating condition of the system. The present invention provides a solid shaft longitudinal of the bore of the slide valve which is subject to fluid pressure from the pilot port to actuate the indicator means.
The present invention seeks to solve the above-named problems by providing a second external housing which protects the slide valve shaft from the effects of the environment and manual abuse by sealingly providing a cover for the internal components and a means for manually resetting the valve. The second external housing also provides a housing for the manual detent means so that it can engage the lip of the main body housing instead of the slide valve shaft itself to provide consistent gripping without wear on the slide valve shaft. Further, the indicator means is encapsulated in the secondary external housing so that it can be easily removed for maintenance or replacement while the control valve remains in operation.
Further, in considering the shortcomings of the prior art devices, it should be noted that many prior art slide valve-actuated indicators are actuated by fluid pressure and due to unequal distribution of fluid and clogging are not capable of giving consistently accurate indictions of the operating conditions of the system. The present invention, by providing a second internal shaft and piston, produces a consistent and reliable visual indication of the operating conditions of the system.
3. Summary of the Invention
The present invention provides for a pilot relay control valve with a visual indicator mounted thereon, the control valve having a main body housing with a bore extending longitudinally thereof for housing a main slide valve with one end portion extending from the main body housing into a secondary housing or cover which provides a protective cover and a means for manually moving the slide valve to a displaced position for setting the control valve as required in the system. In.the main body housing are provided ports that control the flow of fluid in the system and that apply fluid pressure to a first piston means on the other end of the slide valve to move it outwardly. The first piston face is provided with a plurality of holes therein for transmitting fluid pressure to a second interior piston means housed in the first piston means. The second piston means is provided on the end of a shaft which extends throughout the length of the slide valve coaxially therewith. Mounted to the outer end of the coaxial slide valve and shaft is a visual indicator means which uses a two color system to indicate the operating status of the control system. The visual indicator has a two color member movable between two positions for indicating which of two operating conditions exist. In operation, when the second piston is not subject to fluid pressure the visual indicator exposes one colored side and when the second piston means is subject to fluid pressure, movement is imparted to the shaft and the visual indicator exposes the other colored side. A manual detent means is provided in the secondary housing or cover to maintain the slide valve in an out position until a predetermined high pressure is obtained. The manual detent is depressable inwardly to engage a lip portion of the main body housing and hold the slide the valve in its out position until the slide valve is moved out of engagement with the detent.
It is an object of the present invention to provide a pilot relay control valve with dual housing for protection of the slide valve shaft therein.
A further object of the present invention is to provide a control valve in which the main slide valve shaft is sealed from exposure to adverse environmental conditions such as mud, dirt and salt water.
It is a further object of the present invention to provide a means for wiping clean the internal portion of the main body housing when it is to be exposed to adverse environmental conditions.
It is a further object of the present invention to provide a control valve with a slide valve assembly with a manual reset capability, yet reduced susceptibility of the slide valve to bending.
It is a further object of the present invention to provide a manual detent means for setting the control valve in an out position in which the catch or latching pin does not engage the surface of the slide valve but, instead, the lip portion of the main housing to eliminate surface wear of the slide valve.
It is a further object of the present invention to provide a control valve and visual indicator means in which the visual indicator means can be maintained or replaced without a shut down of the control valve operation.
It is a further object of the present invention to provide an internal shaft to actuate the visual indicator means.